1. Field of the Invention
The disclosure of Japanese Patent Application No. 2006-110034 filed on Apr. 12, 2006, including the specification, drawings and abstract is incorporated herein by reference in its entirety.
The present invention relates to a start-up control device and method for an internal combustion engine having either or both of a fuel injection mechanism for injecting fuel into a cylinder at high pressure (in-cylinder injector) and a fuel injection mechanism for injecting fuel into an intake port (intake passage injector), and more particularly to a technique to actuate a fuel pump before cranking.
2. Description of the Related Art
A gasoline engine is known that includes a first fuel injection valve for injecting fuel into a combustion chamber (in-cylinder injector) and a second fuel injection valve for injecting fuel into an intake passage (intake passage injector) and that adjusts the distribution of fuel between the in-cylinder injector and the intake passage injector according to the engine speed or the engine load. A direct-injection gasoline engine that includes only a fuel injection valve for injecting fuel into a combustion chamber (in-cylinder injector) is also known. Besides, a gasoline engine that includes only a fuel injection valve for injecting fuel into an intake passage (intake passage injector) is most traditionally known.
In a high-pressure fuel system which includes the in-cylinder injector, fuel pressurized by a high-pressure fuel pump is supplied to the in-cylinder injector via a delivery pipe, and the in-cylinder injector injects the pressurized fuel into a combustion chamber in each cylinder of the engine.
A diesel engine having a common rail fuel injection system is also known. In the common rail fuel injection system, fuel pressurized by a high-pressure fuel pump is reserved in a common rail, and injected from the common rail into a combustion chamber in each cylinder of the diesel engine, by opening and closing operations of an electromagnetic valve.
In order to pressurize fuel in such engines, a high-pressure fuel pump is used to drive a piston or plunger by means of a cam provided on a drive shaft coupled to a crankshaft of the engine. Engines including only an intake passage injector are not provided with such a high-pressure fuel pump.
When any type of engine including either or both of a in-cylinder injector and an intake passage injector is stopped, left alone and then restarted, a problem as described below occurs.
In any type of engine, piping from the fuel tank to the injector has an oil-tight construction. However, fuel may leak due to a seal failure, or fuel may leak from the injector if a foreign matter is caught in a fuel injection nozzle of the injector. This causes the decrease in the fuel pressure from an engine stop, which causes the fuel to boil under a reduced pressure and thus be vaporized in the piping (when the fuel pressure falls below the saturation fuel vapor pressure of the fuel, although it depends on the fuel temperature).
High-pressure fuel pumps inevitably have a clearance with its pump plunger. When fuel leaks from the clearance, the fuel having leaked is returned to the fuel tank (at atmospheric pressure) through a return pipe. This also causes the decrease in the fuel pressure from the engine stop, which causes the fuel to boil under a reduced pressure and thus be vaporized in the piping.
Such fuel vapor generated in the fuel piping prevents the pressure in the fuel piping from immediately increasing to a feed pressure, thus adversely affecting the startability of the engine. In any type of engine described above, such fuel vapor generation is caused by the decrease in pressure in the fuel piping while the engine is stopped.
JP-A-Hei 06-173806 discloses an injection system for an internal combustion engine that can ensure fuel injection from an injector even if the pressure in fuel piping decreases while the engine is stopped. This injection system for an internal combustion engine has: a fuel injection valve for injecting a desired amount of fuel into an intake passage of the internal combustion engine by appropriately controlling the communication between a supply port and an injection port for fuel; a fuel pump for pumping up fuel from a fuel tank to pressurize the fuel; a fuel path for communication between the fuel injection valve and the fuel pump; and a fuel pressure regulator provided in the fuel path to maintain the pressure of fuel in the fuel path less than a predetermined value. Fuel to be supplied to the fuel supply port of the fuel injection valve is maintained at a constant pressure. The injection system includes: a start-up prediction section for detecting a predetermined event that occurs before start-up of the internal combustion engine to predict start-up of the internal combustion engine based on the detected event; and a fuel pressurization section for increasing the pressure of fuel in the fuel path when start-up of the internal combustion engine is predicted by the start-up prediction section.
According to this injection system for an internal combustion engine, when a predetermined event that occurs before start-up of the internal combustion engine is detected (when it is detected that the door to the driver's seat has been opened by monitoring the open/close state of that door while the internal combustion engine is stopped), the pressure in the fuel path is preliminarily increased so that fuel at a predetermined pressure can be supplied to the fuel injection valve at starting up of the internal combustion engine. Thus, unlike in conventional systems, the fuel injection amount does not become unstable at starting up of the internal combustion engine, thus ensuring excellent startability of the internal combustion engine and excellent operational stability of the vehicle immediately after start-up.
In the injection system for an internal combustion engine disclosed in JP-A-Hei 06-173806 mentioned above, however, the fuel pressure is preliminarily increased when an opening operation of the door to the driver's seat is determined so that the engine is to be started, instead of whether fuel vapor is actually generated or not. If the fuel pump is operated in this way, the operating life of the fuel pump is shortened, and the so-called “NV” (Noise and Vibration) problem is caused by operation of the fuel pump before engine start-up. Even if the fuel pump is actuated only when the door to the driver's seat is opened and the fuel pressure is less than a predetermined pressure, as disclosed in an embodiment (FIG. 4) of the above-mentioned document, the fuel pump could be actuated while fuel vapor is actually not generated.